Piston and staple driver combination



April 14, 1959 H. F. BAKER 2,881,738

PISTON AND STAPLE DRIVER COMBINATION Filed Nov. 29, 1956 INVENTOR.

W WMW PISTGN AND STAPLE DRIVER CONIBINATION Harold F. Baker, Elmhurst, Ill., assignor to Signode Steel Strapping Company, Chicago, 111., a corporation of Delaware Application November 29, 1956, Serial No. 625,131

Claims. (Cl. 121-13) The present invention relates to improvements in pneumatic stapling tools, and in particular to a new and improved arrangement for securing the staple driver to the piston.

Stapling tools of the type to which the present invention pertains include an air cylinder, a piston reciprocable in the cylinder and arranged to drive a staple driver through its power stroke, a magazine for storing a quan tity of staples and having means for feeding staples to be driven by the staple driver into the work, an air valve for controlling the admission of air into and the exhaust of air from the cylinder, and a trigger for manipulating the valve. The invention in the present case relates only to the means by which the piston is connected to the staple driver so that the latter may be driven through its power stroke.

A principal object of the present invention is to provide a new and improved piston and staple driver combination for pneumatic stapling tools, which has all of the advantages of the known combinations wherein the piston is pinned to the driver and with the further advantage that it puts no load on the pin or on the driver at the pin.

Another advantage is to provide a new and improved piston and staple driver combination which has at least as much, and usually more, load transmission area between the piston and the driver as would be the case were the driver to be abutted directly against the inside of the piston head.

Another object is to provide a new and improved piston and staple driver combination which substantially eliminates the driver-piston connection failure.

Another object is to provide a new and improved piston and staple driver combination wherein it is extremely easy to replace a worn staple driver or to change the size of the staple driver by removing one and substituting another.

Another advantage is to provide a new and improved piston and staple driver combination having a minimum number of parts.

Still another object is to provide a new and improved piston and staple driver combination which is simple in construction, extremely rugged, and easy to assemble.

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawings, wherein Fig. 1 is a side elevational view, partially broken into section better to illustrate the invention, of a pneumatic stapling tool incorporating the novel piston and driver combination;

Fig. 2 is an enlarged detail sectional view taken on the line 2-2 of Fig. 1, looking in the direction of the arrows;

Fig. 3 is a horizontal sectional View taken on the line 3-3 of Fig. 2, looking in the direction of the arrows; and

Fig. 4 is a face view, on a smaller scale, of a staple driver made in accordance with the present invention.

tates ate t The pneumatic stapling tool in which the present invention is incorporated is shown in Fig. 1, and is indicated by the reference character 10. It comprises a main casting 12 providing a handle 14 and a cylinder section 16. A staple housing magazine 18 is secured to the casting 12 by a pair of bolts 20. The handle portion of the casting is suitably cored to provide air inlet and exhaust passages, and also a housing for an air control valve 22 which is operated by a trigger 24 pivoted at 26. Air for the operation of the stapler is supplied from a conventional pressurized air supply hose 28 which is connected to the handle by a conventional fitting 30. The staples are driven from the end of the magazine through staple guideway assembly 32 and are urged toward the guideway by a follower 34 under the force of a spring 36.

The cylinder portion 16 of the casting is cored and finished to provide a cylinder 38 in which a piston 40 is reciprocable. The upper or head end of the cylinder 38 is closed by a cap 42 having a plurality of stops 44 thereon defining therebetween air ports 46 which communicate with passageways 48 formed in the casting 12 and through which the air flows. The piston is urged to its retracted position by a return spring 50, the lower end of which acts against the top of the magazine 18, and the upper end of which abuts against the piston 40.

The staples are driven through the staple guideway by a staple driver 54 which is connected to the piston 40 by the novel connecting means of the present invention for movement in both the driving and retracting directions. The movement of the piston 40 is momentarily restrained at the outset of a driving operation by a holdup pawl 56 which detains the piston suificiently long to permit the building up of air pressure at the piston head and then the pawl is released by the trigger 24. The constructional and operational details of the stapling tool 10 are more fully shown and described in the copending application of Arvid I. Ericsson, Serial No. 621,096, filed November 8, 1956, and entitled Pneumatic Stapling Tool and assigned to the assignee of this invention.

As best seen in Fig. 2, the piston 40 is of double cupshaped formation and has a piston head 58 integral with an upwardly extending flange 60 forming an air receiving cup in which a substantial quantity of air under pressure can accumulate prior to the release of the piston by the pawl 56, thereby permitting the piston to be driven through the power stroke by the air under pressure without a substantial pressure drop as would be the case if the piston had the conventional fiat head.

The piston 40 has a depending cylindrical skirt 62 which has a portion thereof immediately below the piston head 58 tapped at 64 preferably with an American Standard tap which may be of eleven threads per inch. Below the tapped portion 64, the skirt 62 is counterbored at 66 to a slightly greater diameter to provide a shoulder 68 between the tapped portion 64 and the counterbored portion 66. This shoulder provides a seat for the upper end of the piston return spring 50, as clearly shown in Fig. 2.

The staple driver 54 is made of fiat steel, preferably spring steel, and has a lower blade portion 70 of a width adapted to fit into the staple guideway 32 and to drive the staples from the end of the magazine and into the work. The blade 70 is, therefore, but slightly wider than the staples for which the stapling tool 10 is designed. The staple driver 54 has a head portion 72 which is wider than the lower or blade portion and is of a width slightly narrower than the toothed portion 64 of the piston skirt. However, at is upper end the edges of the head portion 72 are provided with laterally projecting teeth 74 formed with a profile on the same standard as are the tapped threads 64, in the particular example given, American Standard threads, eleven per inch. The outer edge ends of each of the teeth are cut off to remove the sharp tips. The staple driver 54 is secured to the piston 40 merely by screwing the toothed portion 74 of the staple driver in the tapped portion 64 of the piston skirt.

The load transmission area is, therefore, the sum of the areas of contact in the load transmission direction between the individual teeth 74 and the threads 64, and in the particular embodiment illustrated this area is substantially greater than it would be if the staple driver 54 were to abut its upper edge against the underside of the piston head 58.

A hole 76 is formed in the head 72 of the piston driver 54 between the toothed edges 74. This hole is positioned well within the piston skirt 62 when the staple driver is in place. The piston skirt 62 is provided in the region of the tapped portion thereof with a plurality of diametral holes 78, there being six of these holes '78 as seen in Fig. 3, and they may be formed by diametrically drilling the piston skirt at three difierent positions. A number of holes 78 are provided so that the proper longitudinal adjustment of the driver with respect to the piston can be made. A locking pin 80 is fitted through a pair of holes 78 and the hole 76 in the staple driver 54, thereby preventing relative rotation between the staple driver 54 and the piston 40 and inadvertent separation of the driver from the piston after the piston has been enclosed in the cylinder 38. It is clear from Figs. 2 and 3 that the pin 80 does not carry any of the load when the piston drives the staple driver through its power stroke.

Should it be necessary to replace a worn staple driver 54 with a new one, or to change the staple driver size in converting the stapling tool from one size staple to the other, the piston 40 and staple driver 54 are removed from the cylinder 38 after the cap 42 has been removed. The pin 80 is removed, the staple driver 54 unscrewed, a new one of desired size screwed into place, and the pin 80 is replaced. The combination of piston and driver is then returned to the cylinder and the cap 42 closes the head of the cylinder. The tool is then ready for use.

From the foregoing description it is clear that the objectives which have been claimed for this novel piston and staple driver combination have been attained.

While a preferred embodiment of the piston and staple driver combination constituting this invention has been shown and described, it will be apparent that numerous modifications and variations thereof may be made without departing from the underlying principles of the invention. It is, therefore, desired by the following claims to include within the scope of the invention all such variations and modifications by which substantially the results of this invention may be obtained through the use of substantially the same or equivalent means.

What is claimed as new and desired to be secured by United States Letters Patent is:

1. In a pneumatic stapler having a cylinder, 2. piston reciprocable in the cylinder, and a flat, blade type staple driver to be driven by the piston, the combination comprising an internally tapped piston skirt on the piston and attached to the piston head, a flat head on the staple driver having toothed edges at the opposite sides thereof complementary to the tapped skirt and screwed into the tapped piston skirt, an opening in the staple driver head, a plurality of diametral openings in the piston skirt in the tapped portion thereof, and a pin extending through a pair of skirt openings and said driver opening to prevent relative rotational movement between the piston and the staple driver.

2. In a pneumatic stapler having a cylinder, a piston reciprocable in the cylinder, and a flat, blade type staple driver to be driven by the piston, the combination comprising an internally tapped piston skirt on the piston and integral with the piston head, a fiat head on the staple driver, the opposite side edges of said stapler driver head complementary to the tapped skirt by means of which said driver head being formed with teeth is screwed into said tapped piston skirt so as to secure the staple driver to the piston, and means engageable with the driver and the piston to lock the driver and the piston against relative rotational movement.

3. In a pneumatic stapler having a cylinder, a piston reciprocable in the cylinder, and a staple driver of the flat blade type to be driven by the piston, the combination comprising an internally tapped piston skirt on the piston and integral with the piston head, a flat head on the staple driver, and toothed edges on said staple driver head complementary to the tapped skirt by means of which said driver head is screwed into said tapped piston skirt so as to secure the staple driver to the piston.

4. In a pneumatic stapler having a cylinder, a piston reciprocable in the cylinder, and a flat blade staple driver to be driven by the piston, the combination comprising a piston skirt on the piston and attached to the piston head, a flat, blade-like head on the staple driver, interfitting means on the opposite edges of said staple driver head and on the inner walls of said piston skirt to secure the driver to the piston, an opening in the staple driver head, a pair of diametral openings in the piston skirt, and a pin extending through said pair of skirt openings and said driver opening to prevent relative movement between the piston and the staple driver.

5. In a pneumatic stapler having a cylinder, a piston reciprocable in the cylinder, and a flat blade staple driver to be driven by the piston, the combination comprising a piston skirt on the piston and attached to the piston head, a fiat, blade type head on the staple driver, interfitting means on the opposite edges of said staple driver head and on theinner walls of said piston skirt to prevent only longitudinal movement of the driver relative to the piston and to secure the driver to the piston, and means preventing rotational movement of the driver relative to the head thereby to lock the driver to the piston.

References Cited in the file of this patent UNITED STATES PATENTS 2,445,674 Kendall July 20, 1948 2,682,052 Juilfs June 29, 1954 2,682,658 Hoefiich July 6, 1954 2,687,522 Juilfs Aug. 31, 1954 2,703,557 Polki Mar. 8, 1955 2,714,207 Lindstrom Aug. 2, 1955 2,756,723 Bassinger July 31, 1956 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2,881,738 April 14, 1959 Harold E. Baker It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2., line 68, for "at is" read at its column 4, line 14-, strike out "being formed with teeth. and insert the same after "head" in line 13;, same column; same column 4., line 46-,- for "Walls." read me Well Signed and. sealed this 11th day of August 1959 (SEAL) Attest:

KARL E. AXLINE Attesting Oflicer ROBERT C. WATSON Commissioner of Patents 

